Advancements in photodetector technology, especially in the infrared (IR) photodetector arena, has led to the integration of single element detectors operating in photovoltaic mode into multi-element linear arrays, 2D arrays on Silicon read-out circuits, and very large focal plane arrays (FPAs) having upwards of millions of photodetector elements.
The advent of multi-band detectors, such as stacked (or back-to-back) photovoltaic detectors, has greatly simplified the design of dual-band or multi band image sensors and photodetector devices, which are highly desirable in many civil and military applications, such as target detection systems.
Current dual-band vision systems are limited by the fact that dual-band FPAs employing stacked (or back-to-back) bias-selectable photovoltaic detectors are, at any given time, capable of operating either in a first spectral band or a second spectral band, but not both simultaneously. Therefore, one existing method for capturing an image in two separate colors (or spectral bands) involves the use of time division multiplexing (TDM) to create the perception of temporally simultaneous two-color detection. Using this approach, the array captures light of a first spectral range for a period of time (e.g., 100 μs) and then the entire array switches to capturing light of a second spectral band for another period of time. However, this approach does not appear to yield the desired performance (sensitivity) that is required in high speed detection systems, such as those used on missile warning systems on planes.
Accordingly, what is desired is a high speed multi-band detection system capable of capturing light at different spectral bands in a temporally simultaneous and (nearly) spatially coincident manner.
Further, given the difficulty of manufacturing a faultless detector array operating in the IR range; what is desired is a multi-band detection system that is fault tolerant without sacrificing overall system operability.